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Large suburban and bush Tasmanian Blue Gums (Eucalyptus globulus) and Black Gums (Eucalyptus ovata) in Mount Nelson, Tasmania, as foraging resources for the endangered Swift Parrot (Lathanzus discolor)


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Piech, M 2009 , 'Large suburban and bush Tasmanian Blue Gums (Eucalyptus globulus) and Black Gums (Eucalyptus ovata) in Mount Nelson, Tasmania, as foraging resources for the endangered Swift Parrot (Lathanzus discolor)', Research Master thesis, University of Tasmania.

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Remnant trees in suburban areas constitute potential habitat for vertebrates by
providing food and nesting sites. Trees, including the Tasmanian Blue Gum
(Eucalyptus globulus) and Black Gum (E. ovata), are known to supply nectar and
pollen to the endangered Swift Parrot (Lathamus discolor), whose breeding success
depends on flowering of these two eucalypt species. The outer Hobart suburb of
Mount Nelson, Tasmania, is one of the foraging grounds that the Swift Parrot utilises
during its breeding season.
The aim of the project was to investigate the relative value of large
E. globulus and E. ovata in the bush and suburban areas of Mount Nelson as foraging
habitat for Swift Parrots, and to examine which characteristics of the trees and their
location affected flower production. In addition, the study investigated the recent and
current trends of tree removal from private properties, as well as future plans for tree
felling, in order to determine whether the forage sources for the Swift Parrot are
declining within the suburb.
From a sample of 261 randomly selected large E. globulus and E. ovata trees
( greater than 60 cm in diameter at breast height) in Mount Nelson, it was found that suburban
trees produced more flowers than their edge or bush counterparts. Hence, the former
are more reliable nectar and pollen sources for a range of nectarivorous birds,
including the Swift Parrot. It is thus argued that suburban trees do not just provide a
secondary (to bushland) food supply for Swift Parrots, but constitute an important
foraging habitat in their own right outside bush areas. Bush trees, however, despite
being less important in providing food to the Swift Parrot, were more likely to
support a greater number of nesting hollows for the species.
The study found that the abundance of flowers produced was significantly
related to a number of tree variables. Trees with denser canopies, of better health,
with no or a low percentage of branches in the canopy that were dead, and no fire
damage were likely to support more flowers. The impact of fire was at least partially
mediated via its effect on increasing tree dieback and the percentage of branches that
were dead, and to a lesser degree, reducing canopy density. A survey of Mount Nelson residents suggests that many large E. globulus and
E. ovata occur on private unprotected land of Mount Nelson. However, they are
rapidly being removed. An estimated 28.8% of all large E. globulus declared in the
survey and 29.9% of E. ovata have either been removed in the past five to ten years,
or will be removed in the near future. Hence, the amount of food available to Swift
Parrots in Mount Nelson is being reduced. There is thus a need to retain these
valuable tree resources. Maintaining trees in the suburbs as foraging habitat, as well
as trees in the bush as nesting habitat, could be important for the long-term survival
of the Swift Parrot.

Item Type: Thesis - Research Master
Authors/Creators:Piech, M
Keywords: Eucalyptus globulus, Eucalyptus ovata, Tasmania, swift parrot, nutrition, foraging habitat, suburban trees
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